Why We Get Fat

By Kara Carper, MA, CNS, LN
October 3, 2012


According to the Centers for Disease Control, almost 70% of Americans are overweight (35% fall into the obese category). With all the weight loss programs, diet foods, exercise tips, and experts looking for solutions to the obesity epidemic, why is the rate of obesity getting worse?

The real cause of obesity

If losing weight were as simple as “eat less, exercise more,” you would think we would have this problem mastered by now. Science journalist and author Gary Taubes understands why these fundamental nutrition beliefs are wrong. In his latest book, Why We Get Fat and What to Do About It, Mr. Taubes summarizes two centuries of research he analyzed for his previous book, Good Calories Bad Calories. His new book is a quicker and easier read based on the premise that excess sugar and carbohydrates cause fat storage.

Let's take a closer look at the argument that excess sugar and carbohydrates cause fat storage. When you eat carbohydrates, your blood sugar goes up. When your blood sugar goes up, a hormone called insulin is secreted to lower the blood sugar.

Carbohydrates that cause a dramatic rise in blood sugar and require a lot of insulin include the following:

  • Pasta, bread, crackers, bagels, muffins, chips, cereal, potatoes, rice, desserts (cookies, cake, candy)

Carbohydrates that don't require a lot of insulin include these vegetables:

  • Leafy greens, broccoli, cauliflower, green beans, tomatoes, asparagus (yes, vegetables ARE carbohydrates)

Insulin is a fat-storing hormone, which is why excess carbohydrates and sugars you consume cause fat storage in your body. Eating a bagel that contains 57 grams of carbohydrates (14 ½ teaspoons sugar) keeps your body so busy burning all of those carbohydrates that it seldom gets around to burning stored fat! The fat remains stored while your body works as a carbohydrate/sugar burner. Stored fat can be burned when your glucose levels (blood sugar) decrease. This explains why eating two cups of steamed vegetables with 15-20 grams of carbohydrates (only 4-5 teaspoons sugar) allows fat to be burned.

Nell’s success story

A client of mine, Nell Kauls, has lost 90 pounds by following a low-carb eating plan. At first the weight loss was a struggle. Once she realized how carbohydrate-sensitive her body was and modified her eating plan accordingly, the weight started coming off. Nell has eliminated all grains, and reduced her intake of starchy vegetables (corn, peas, potatoes, carrots)—all of these are carbohydrates that require higher levels of insulin to normalize blood sugar.

Listen to Nell Kauls on Dishing Up Nutrition from January 8, 2011 and January 14, 2012.

The secret to weight loss: the right kind and quantity of carbs

For people that are insulin-resistant and pre-diabetic, it's often necessary to greatly reduce carbohydrate consumption to stabilize blood sugars, lower insulin levels, and lose weight. You may get confused about low-carb eating and think it's a fad or the latest trend. When we recommend low-carb eating, keep in mind that we still include some fruits like berries and non-starchy vegetables, such as the vegetables listed above. Starchier vegetables like carrots, corn, peas and potatoes need to be eaten in moderation (½ cup serving cooked). For some people, they need to be eliminated for weight loss.

You may be thinking: “If I can't eat starchy carbohydrates on my weight loss plan, what can I eat?” You can eat protein, fat, non-starchy vegetables, and some fruits! Imagine sitting down to a meal of a four-ounce, grass-fed hamburger with one ounce of cheese (hold the bun), and a salad containing three cups of mixed greens, tomatoes, peppers, mushrooms, one tablespoon of full-fat dressing, a few kalamata olives, and half a cup of fresh raspberries on the side. This is a fat-burning meal. However, eating that same cheeseburger with the bun and French fries in place of the salad and berries, would create an insulin surge resulting in fat being stored instead of being burned.

Good fats are essential for weight loss

You may be thinking: “But I thought fat would make me fat and keep me from losing weight!” Gary Taubes to the rescue again. His book advocates eating fat, which has minimal impact on blood sugar and insulin. Of course, not all fats are the same, and it's important to choose good fats. Healthy fats for optimal metabolism include olive oil, butter, coconut oil, nuts, seeds, nut butters, avocadoes, and olives. Unhealthy fats that actually slow metabolism and should be eliminated include soybean, cottonseed, sunflower, canola and other vegetable oils, as well as any hydrogenated oils and man-made fats.


About the author

Kara knows the power of real food to heal almost any health concern—from anxiety to weight loss. She discovered the power of food for herself when she used nutrition to heal her insomnia. Kara received her M.A. in holistic health studies at the University of St. Catherine with an emphasis in herbology. She is nationally recognized as a certified nutrition specialist through the American College of Nutrition and is a licensed nutritionist through the Minnesota Board of Dietetics and Nutrition.

View all posts by Kara Carper, MA, CNS, LN


I was advised to not eat a low carb diet because it affected my thyroid negatively.. The main reason why carbs affect thyroid function so directly is because insulin is needed for the conversion of the inactive T4 hormone into the active T3 hormone. My hypothyroidism is worse on a low carb diet and causes weight gain.
October 7, 2016 at 8:49 pm


Yes, it is important to make sure to get enough carbohydrates for thyroid function. Having a 1/2 c.of starch or fruit every time you eat is probably not too low of carb for your thyroid function. When it comes to nutrition everybody has individual needs. There’s no one size fits all plan. 

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